Embedding a nanotube inside a nanopore for dna translocation

ABSTRACT

A technique for embedding a nanotube in a nanopore is provided. A membrane separates a reservoir into a first reservoir part and a second reservoir part, and the nanopore is formed through the membrane for connecting the first and second reservoir parts. An ionic fluid fills the nanopore, the first reservoir part, and the second reservoir part. A first electrode is dipped in the first reservoir part, and a second electrode is dipped in the second reservoir part. Driving the nanotube into the nanopore causes an inner surface of the nanopore to form a covalent bond to an outer surface of the nanotube via an organic coating so that the inner surface of the nanotube will be the new nanopore with a super smooth surface for studying bio-molecules while they translocate through the nanotube.

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY CLAIM

This application is a continuation of U.S. Non-Provisional applicationSer. No. 13/228,491, entitled “EMBEDDING A NANOTUBE INSIDE A NANOPOREFOR DNA TRANSLOCATION”, filed Sep. 9, 2011, which is incorporated hereinby reference in its entirety.

BACKGROUND

Exemplary embodiments relate to nanodevices, and more specifically, toproviding a smooth inner surface for a nanopore by fixing a nanotubeinside the nanopore.

Recently, there has been growing interest in applying nanopores assensors for rapid analysis of biomolecules (e.g., polymers) such asdeoxyribonucleic acid (DNA), ribonucleic acid (RNA), protein, etc.Emphasis has been given to applications of nanopores for DNA sequencing,as this technology holds the promise to reduce the cost of sequencingbelow $1000/human genome.

Nanopore sequencing is a technique for determining the order in whichnucleotides occur on a strand of DNA. A nanopore is simply a small holeof the order of several nanometers in internal diameter. The theorybehind nanopore sequencing has to do with what occurs when the nanoporeis immersed in a conducting fluid and an electric potential (voltage) isapplied across it: under these conditions, a slight electric current dueto conduction of ions through the nanopore can be measured, and theamount of current is very sensitive to the size and shape of thenanopore. If single bases or strands of DNA pass (or part of the DNAmolecule passes) through the nanopore, this can create a change in themagnitude of the current through the nanopore. Other electrical oroptical sensors can also be put around the nanopore so that DNA basescan be differentiated while the DNA passes through the nanopore.

BRIEF SUMMARY

According to an exemplary embodiment, a method of embedding a nanotubein a nanopore is provided. The method includes configuring a reservoirincluding a membrane separating the reservoir into a first reservoirpart and a second reservoir part, where the nanopore is formed throughthe membrane for connecting the first and second reservoir parts. Themethod includes filling the nanopore, the first reservoir part, and thesecond reservoir part with an ionic fluid, where a first electrode isdipped in the first reservoir part and a second electrode is dipped inthe second reservoir part. Also, the method includes driving thenanotube into the nanopore using a voltage bias being applied to thefirst and second electrodes, to cause an inner surface of the nanoporeto form a covalent bond to an outer surface of the nanotube via anorganic coating.

Additional features are realized through the techniques of the presentdisclosure. Other systems, methods, apparatus, and/or computer programproducts according to other embodiments are described in detail hereinand are considered a part of the claimed invention. For a betterunderstanding of exemplary embodiments and features, refer to thedescription and to the drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features of the presentdisclosure are apparent from the following detailed description taken inconjunction with the accompanying drawings in which:

FIG. 1 depicts a cross-sectional schematic of a nanodevice with ananopore embedded with a carbon nanotube according to an exemplaryembodiment.

FIG. 2A illustrates an approach to embed a carbon nanotube inside ananopore of a nanodevice according to an exemplary embodiment.

FIG. 2B illustrates the carbon nanotube attached/bonded to the inside ofthe nanopore according to an exemplary embodiment.

FIG. 2C illustrates the carbon nanotube attached to the inside of thenanopore after processing according to an exemplary embodiment.

FIG. 3A illustrates another approach to embed a carbon nanotube inside ananopore of a nanodevice according to an exemplary embodiment.

FIG. 3B illustrates the carbon nanotube attached/bonded to the inside ofthe nanopore according to an exemplary embodiment.

FIG. 3C illustrates the carbon nanotube attached to the inside of thenanopore after processing according to an exemplary embodiment.

FIG. 4A illustrates an additional approach to embed a carbon nanotubeinside a nanopore of a nanodevice according to an exemplary embodiment.

FIG. 4B illustrates the carbon nanotube attached/bonded to the inside ofthe nanopore according to an exemplary embodiment.

FIG. 4C illustrates the carbon nanotube attached to the inside of thenanopore after processing according to an exemplary embodiment.

FIG. 5 is a method for embedding a nanotube inside a nanopore accordingto an exemplary embodiment.

DETAILED DESCRIPTION

An issue in DNA sequencing is to control the translocation of the DNAthrough the nanopore. The surface roughness of the nanopore and thedangling bonds on the surface of the nanopore may present problems forDNA sequencing. After drilling a solid-state nanopore using an electronbeam, the pore surface may exhibit nanometer scale corrugations (e.g.,folds, wrinkles, groves, etc.). Similar to the scaling behavior of aself-affine rough surface, the smaller a nanopore is the rougher theinner pore surface is. Additionally, nanopores drilled using the sameprocedure may have different surface roughness, causing each pore to beunique. Thus, experiments that are performed using nanopores with roughsurfaces and/or dangling bonds may likely (or may possibly) showinconsistent results because of the unpredictable interactions betweenDNA and the inner surface of the nanopore. For example, simulations showthat the effective electric driving forces on DNA are different if thesurface roughness of the same-sized nanopores is different.

Exemplary embodiments are configured to attach carbon nanotubes at theinner surface of the nanopore and leverage the smoothness of the innersurface of carbon nanotubes. This approach can eliminate the physicalsurface roughness as well as the dangling bonds at the inner surface ofthe nanopore, which are the sources of unpredictable interactionsbetween DNA and the inner surface of the nanopore. Additionally, thechemical inertness of carbon nanotubes will be a potential benefit, suchas by protecting the metal electrodes employed at the inner surface ofthe nanopore.

Now turning to the figures, FIG. 1 depicts a cross-sectional schematicof a nanodevice 100 with a nanopore embedded with a carbon nanotubeaccording to an exemplary embodiment. The nanodevice 100 illustrates aDNA translocation setup. A membrane 150 is made of one or moreinsulating films 101 with a nanopore 103 formed through the insulatingfilm 101. A carbon nanotube 102 is embedded at the inner surface of thenanopore 103. The insulating film 101 of the membrane 150 partitions areservoir 104 into two reservoir parts, which are reservoir part 105 andreservoir part 106. The reservoir 104 (including reservoir parts 105 and106) and the nanopore 103 are then filled with ionic buffer/fluid 107(e.g., such as a conductive fluid).

A polymer 108 such as a DNA molecule(s) is loaded into the nanopore 103by an electrical voltage bias of the voltage source 109, which isapplied across the nanopore 103 via two electrochemical electrodes 110and 111. The electrodes 110 and 111 are respectively dipped in the ionicbuffer 107 of the reservoir part 105 and the reservoir part 106 in thereservoir 104.

There are various state of the art techniques for sensing DNA bases andcontrolling the motion of the DNA, and the roughness and the danglingbonds in a regular (state of the art) nanopore may pose a potentialproblem. However, the smooth inner surface of the nanotube 102 willprovide a (very) smooth surface with no dangling bonds forcharacterization (i.e., nanopore sequencing of the DNA) and movement ofthe polymer 108.

There may be many techniques with many different materials that can beutilized to make the nanodevice 100 shown in FIG. 1. According to anexemplary embodiment, FIGS. 2A, 2B, and 2C illustrate one approach toembed a carbon nanotube inside a nanopore of a nanodevice 200 such as achip. FIGS. 2A, 2B, and 2C depict a cross-sectional schematic of thenanodevice 200. In FIG. 2A, a membrane 250 includes a substrate 201(e.g., such as silicon), between membrane parts 202 and 203. Themembrane parts 202 and 203 may be made of a material (such as Si₃N₄(silicon nitride)) with a high etching selectivity with respect to thesubstrate 201. The membrane part 202 may also contain other materiallayers, such as metal layers, etc., for any desired application. Awindow 255 is opened into the membrane part 203 using, e.g., reactiveion etching, and the substrate 201 will be etched through to themembrane part 202; etching through the window 255 of the membrane part203 as well as through the substrate 201 will form a free-standingmembrane part 260 of the membrane part 202. In the case of a siliconsubstrate for the substrate 201, the etchant could be KOH (potassiumhydroxide) or TMAH (tetramethylammonium hydroxide) at 80° C. A nanopore207 is made/formed through the free-standing membrane part 260 of themembrane part 202. The membrane 250 (including the free-standingmembrane part 260) partitions a reservoir 208 into reservoir part 209and reservoir part 210. The reservoir 208 (including reservoir parts 209and 210) and the nanopore 207 formed through membrane part 202 are(then) filled with ionic buffer/fluid 211. The nanopore 207 is a smallaperture formed in, e.g., the free-standing membrane part 260 of themembrane part 202.

As shown in FIG. 2A, the outer surface of a carbon nanotube 204 can becoated with an organic coating 205. The organic coating 205 isconfigured to be covalently bonded to the inner surface of the nanopore207. The organic coating 205 and/or the carbon nanotube 204 is charged(by tuning the pH of the ionic buffer 211), such that the carbonnanotube 204 can be transported/driven into the nanopore 207 by thevoltage source 109 applying a voltage bias to electrodes 110 and 111,and then the carbon nanotube 204 can be covalently bonded to the innersurface of the nanopore 207, as shown in FIG. 2B. Alternatively and/oradditionally, a fluidic pressure adjustment device 280 can becommunicatively connected to the reservoir part 210 via a port 282, anda fluidic pressure adjustment device 285 can be communicativelyconnected to the reservoir part 209 via another port 284 in oneimplementation. To drive the carbon nanotube 204 (which can be chargedor uncharged) into the nanopore 207, the fluidic pressure adjustmentdevice 280 is configured to apply a positive fluidic pressure to thereservoir part 210 and/or the fluidic pressure adjustment device 285 isconfigured to apply a negative fluidic pressure to the reservoir part209. The carbon nanotube 204 is driven into the nanopore 207 by thedifference in fluidic pressure on both sides of the membrane 250 causedby fluidic pressure adjustment device 280 and 285. Also, the carbonnanotube 204 can be driven into the nanopore 207 by the positive fluidicpressure of the fluidic pressure adjustment device 280 alone or by thenegative fluidic pressure of the fluidic pressure adjustment device 285alone. The fluidic pressure adjustment devices 280 and 285 may be pumpsor syringes respectively linked via ports 282 and 284 to the reservoirparts 210 and 209 to apply the desired pressure.

The ionic buffer 107 and 211 in the reservoirs 104 and 208 can be anysalt dissolved in any solvent (water or organic solvent) with any pHdepending on the application. One example of the ionic buffer 107 and211 includes a KCl (potassium chloride) solution in water with a pHrange from 6-9 for DNA translocation. Accordingly, the electrodes 110and 111 can be any electrodes for electrochemical reactions that matchthe salt and solvent. For example, Ag/AgCl electrodes can be a goodmatch for the KCl solution in water.

As discussed further below, the organic coating 205 is a material havingchemical properties that cause the organic coating 205 (applied to thecarbon nanotube 204) to covalently bond to the inner surface material ofthe nanopore 207. As a result of the covalent bond, the carbon nanotube204 is securely attached to the nanopore 207.

Once the carbon nanotube 204 is attached to the inner surface ofnanopore 207, both sides (e.g., top and bottom) of the membrane 250(including the attached nanotube 204) can be processed/etched with O₂(oxygen) plasma to tailor (e.g., remove) the parts of the carbonnanotube 204 that are extending outside of the nanopore 207, as shown inFIG. 2C. In FIG. 2C, the height of the carbon nanotube 204 (e.g., thetop and bottom) is aligned with the height of the membrane part 202after the O₂ plasma processing. The polymer 108 (shown in FIG. 1) may bedriven into the carbon nanotube 204 attached to the nanopore 207 forsequencing by a nanopore sequencer (not shown), and the sequencingoccurs in the nanopore 207 (formed by the carbon nanotube 204) asunderstood by one skilled in the art.

Oxygen plasma etching is a form of plasma processing used to fabricateintegrated circuits. As understood by one skilled in the art, itinvolves a high-speed stream of glow discharge (plasma) of anappropriate gas mixture being shot (in pulses) at a sample, such as atthe membrane 250. Although plasma etching is described, it iscontemplated that other types of etching may be utilized as understoodby one skilled in the art.

FIGS. 3A, 3B, and 3C illustrate another approach to embed a carbonnanotube inside a nanopore according to an exemplary embodiment. FIGS.3A, 3B, and 3C depict a cross-sectional schematic of the nanodevice 300.

In FIGS. 3A, 3B, and 3C, the inner surface of the nanopore 207 is coatedwith the organic coating 215, which can bond to the carbon nanotube 204.The description for FIGS. 3A, 3B, and 3C are the same as for FIGS. 2A,2B, and 2C, except that the carbon nanotube 204 is initially uncoatedbecause the coating is applied to the inner surface of the nanopore 207,instead of on the carbon nanotube 204 (itself). The organic coating 215in FIGS. 3A, 3B, and 3C may be the same material as the organic coating205 in FIGS. 2A, 2B, and 2C in one implementation, and may be differentmaterials in another implementation.

In FIG. 3A, the membrane 250 includes the substrate 201, betweenmembrane parts 202 and 203, and window 255 is opened/etched into themembrane part 203 through the substrate 201 to the membrane part 202 toform the free-standing membrane part 260 of the membrane part 202, asdiscussed above. The nanopore 207 is made/formed through thefree-standing membrane part 260. The membrane 250 (including thefree-standing membrane part 260) partitions a reservoir 208 intoreservoir part 209 and reservoir part 210. The reservoir 208 (includingreservoir parts 209 and 210) and the nanopore 207 formed throughmembrane part 202 are then filled with ionic buffer/fluid 211 asdiscussed above.

Unlike FIG. 2A, the outer surface of the carbon nanotube 204 is notcoated with the organic coating 205 in FIG. 3A. Instead, the innersurface of the nanopore 207 is coated with the organic coating 215. Theorganic coating 215 is configured to covalently bond to the outersurface of the uncoated carbon nanotube 204. If the carbon nanotube 204is charged (by tuning the pH of the ionic buffer 211 filling thereservoir 208), the carbon nanotube 204 can be transported into thenanopore 207 by a voltage bias applied to electrodes 110 and 110 via thevoltage source 109. Also, the carbon nanotube 204 can be driven into thenanopore 207 by the difference in fluidic pressure on both sides of themembrane 250 applied by positive and negative pressures of the fluidicpressure adjustment devices 280 and 285. Once the carbon nanotube 204 isdriven into the nanopore 207, the carbon nanotube 204 can be covalentlybonded to the inner surface of the nanopore 207 via the organic coating215, as shown in FIG. 3B. The organic coating 215 is a material havingchemical properties that cause the organic coating 215 (applied to thenanopore 207) to covalently bond to the outer surface material of theuncoated carbon nanotube 204. As a result of this covalent bond, thecarbon nanotube 204 is securely attached to the nanopore 207.

Once the carbon nanotube 204 is attached to the inner surface ofnanopore 207, both sides of the membrane 250 (including the attachednanotube 204) can be processed with O₂ plasma to tailor (e.g., remove)the extending parts of the carbon nanotube 204 that extend outside ofthe nanopore 207, as shown in FIG. 3C. In FIG. 3C, the height of thecarbon nanotube 204 is aligned to the height of the membrane part 202after O₂ plasma processing. The polymer 108 (shown in FIG. 1) may bedriven into the carbon nanotube 204 attached to the nanopore 207 forsequencing as understood by one skilled in the art.

FIGS. 4A, 4B, and 4C illustrate an additional approach to embed a carbonnanotube inside a nanopore according to an exemplary embodiment. FIGS.4A, 4B, and 4C depict a cross-sectional schematic of the nanodevice 400which illustrates a combination of the approaches discussed in FIGS. 2A,2B, 2C, 3A, 3B, and 3C.

In FIGS. 4A, 4B, and 4C, the inner surface of the nanopore 207 is coatedwith an organic coating 206, while the outer surface of the carbonnanotube 204 is coated with the organic coating 205. The organic coating205 is chemically configured to covalently bond to the organic coating206. Additionally, the organic coating 205 is chemically configured tobond to the carbon nanotube 204, and the organic coating 206 ischemically configured to bond to the inner surface of the nanopore 207.The organic coating 205 is different from the organic coating 206 in oneimplementation. In another implementation, the organic coating 205 canbe the same material as the organic coating 206.

When the organic coating 205 and/or carbon nanotube 204 is charged (bytuning the pH of the ionic buffer), the carbon nanotube 204 can betransported into the nanopore 207 by a voltage bias applied toelectrodes 110 and 110 via the voltage source 109. Also, the carbonnanotube 204 can be driven into the nanopore 207 by the difference influidic pressure on both sides of the membrane 250 applied by thepositive and negative pressures of the fluidic pressure adjustmentdevices 280 and 285. Once the carbon nanotube 204 coated in the organiccoating 205 is driven into the nanopore 207 coated in the organiccoating 206, the carbon nanotube 204 can be covalently bonded to theinner surface of the nanopore 207 via the organic coatings 205 206, asshown in FIG. 4B. The organic coating 205 is a material having chemicalproperties that cause the organic coating 205 (applied to the carbonnanotube 204) to covalently bond to the outer surface material of thecarbon nanotube 204 and to the organic coating 206. Similarly, theorganic coating 206 is a material having chemical properties that causethe organic coating 206 (applied to the nanopore 207) to covalently bondto the outer surface material of the carbon nanotube 204 and to theorganic coating 205. As a result of the covalent bonding, the carbonnanotube 204 is securely attached to the nanopore 207.

As mentioned above, once the carbon nanotube 204 is attached to theinner surface of nanopore 207, both sides of the membrane 250 (includingthe attached nanotube 204) can be processed with O₂ plasma to tailor(e.g., remove) the extending parts of the carbon nanotube 204 thatextend outside of the nanopore 207, as shown in FIG. 4C. In FIG. 4C, theheight of the carbon nanotube 204 is aligned to the height of themembrane part 202 after O₂ plasma processing. In one implementation, theheight of the carbon nanotube 204 may be slightly less than, more than,or about the same as the height of the membrane part 202 (forming thenanopore 207) based on the desired precision of the O₂ plasmaprocessing. The polymer 108 (shown in FIG. 1) may be driven into thecarbon nanotube 204 attached to the nanopore 207 for sequencing asunderstood by one skilled in the art.

Although exemplary embodiments described above may be directed to carbonnanotubes, it should be appreciated that the disclosure is notrestricted to nanopores with carbon nanotubes. Rather, exemplaryembodiments may be applicable for attaching other types of nanotubes tothe inside surface of nanopores utilizing the techniques as discussedherein. Additionally, exemplary embodiments are not limited to embeddingnanotubes into nanopores, and nanotubes may be embedded into otherstructures such as vias, nanochannels, etc., as understood by oneskilled in the art.

FIG. 5 illustrates a method 500 for embedding a nanotube in a nanoporein accordance with an exemplary embodiment. Reference can be made toFIGS. 1, 2A, 2B, 2C, 3A, 3B, 3C, 4A, 4B, and 4C.

A reservoir (e.g., reservoir 104, 208) is configured to include amembrane (e.g., membrane 150, 250) separating the reservoir into a firstreservoir part (e.g., reservoir part 105, 210) and a second reservoirpart (e.g., reservoir part 106, 209) in which the nanopore (e.g.,nanopore 103, 207) is formed through the membrane for connecting thefirst and second reservoir parts at block 505.

The nanopore, the first reservoir part, and the second reservoir partare filled with an ionic fluid (e.g., ionic fluid 107, 211) at block510. A first electrode (e.g., electrode 110) is dipped in the firstreservoir part at block 515, and a second electrode (e.g., electrode111) is dipped in the second reservoir part at block 520.

At block 525, the nanotube is driven into the nanopore to cause an innersurface of the nanopore (e.g., nanopore 103, 207) to form a covalentbond to an outer surface of the nanotube (e.g., nanotube 102, 204) viaan organic coating (e.g., organic coating 205, 206, 215), in response toa voltage bias being applied (e.g., by the voltage source 109) to thefirst and second electrodes (e.g., electrodes 110 and 111). Also, thecarbon nanotube 204 can be driven into the nanopore 207 by thedifference in fluidic pressure on both sides of the membrane 250 appliedby the positive and negative pressures of the fluidic pressureadjustment devices 280 and 285.

The inner surface of the nanopore 207 may be coated with the organiccoating (e.g., organic coating 215 in FIG. 3A or organic coating 206 inFIG. 4A) to form the covalent bond to the outer surface of the nanotube204. Also, the outer surface of the nanotube 204 may be coated with theorganic coating 205 to form the covalent bond to the inner surface ofthe nanopore 207.

In one case, both the inner surface of the nanopore 207 and the outersurface of the nanotube 204 are coated with the organic coating (e.g.,the organic coatings 205 and 206 may be the same material in FIGS. 4A,4B, and 4C), such that the organic coating on the inner surface of thenanopore 207 and the organic coating on the outer surface of thenanotube 204 cause the covalent bond in response to the voltage source109 driving the nanotube 204 into the nanopore 207.

In another case, the inner surface of the nanopore 207 is coated withthe organic coating and the outer surface of the nanotube is coated withanother organic coating (e.g., the organic coatings 205 and 206 may bedifferent materials in FIGS. 4A, 4B, and 4C), such that the organiccoating on the inner surface of the nanopore and the other organiccoating on the outer surface of the nanotube cause the covalent bond inresponse to the voltage source 109 driving the nanotube into thenanopore.

The covalent bond via the organic coating causes the nanotube 102, 204to be physically attached to the nanopore 103, 207 formed in themembrane 150, 250, and both sides (e.g., top and bottom) of the membrane150, 250 are processed such that a height of the nanotube corresponds toa height of a layer (e.g., membrane part 202) of the membrane 250 asshown in FIGS. 2C, 3C, and 4C.

For explanatory purposes, various examples of the organic coatings 205,206, and 215 are discussed below. It is understood that the chemicalmolecules of the organic coatings 205, 206, and 215 discussed below arenot meant to be limited.

The organic coating 205 can be prepared by reaction of aryldiazoniumsalts with the carbon nanotube 204. In this reaction, the diazoniumsalts are reduced by electron transfer from the carbon nanotube 204 todiazonium salts and results in the expulsion of one molecule of nitrogenand formation of a carbon-carbon bond between aryl compound and thecarbon nanotube 204. This is a widely used reaction forfunctionalization of carbon nanotubes with a variety of aryl compoundsmainly because of the simplicity of the reaction and the wide range ofarydiazonium salts available through their corresponding arylamines. Thereaction of aryldiazonium salts with the carbon nanotube 204 takes placeeither in aqueous solution or an organic solvent like dichloroethane,chloroform, toluene, dimethylformamide, etc. The reaction ofaryldiazonium salts with the carbon nanotube 204 is very fast (e.g.,completed within a few minutes) and takes place at room temperature. Thepreferred, but not required, diazonium salts are those with anadditional functionality which can form strong bonds with metal oxidesor nitrides inside the nanopore 207. The additional functionality (toform strong bonds with metal oxides or nitrides inside the nanopore 207)can be chosen from carboxylic acids (—CO₂H), hydroxamic acids (—CONHOH),or phosphonic acids (—PO₃H₂).

In FIGS. 3A, 3B, and 3C, the organic coating 215 is a bifunctionalcompound/molecule in which one functionality is a diazonium salt and theother functionality can be chosen from hydroxamic acid or phosphonicacid. When the nanopore 207 with inside walls of metal oxide or metalnitride is immersed in a solution of this bifunctionalcompound/molecule, the inner surface of the nanopore 207 is coated withthe self-assembled monolayer of this bifunctional compound/moleculethrough hydroxamic acid or phosphonic acid functionality and exposes thediazonium functional group; the diazonium functional group can reactwith the uncoated carbon nanotube 204 (as shown in FIGS. 3B and 3C) toform a covalent bond, therefore immobilizing the carbon nanotube 204inside the nanopore 207.

In FIGS. 4A, 4B, and 4C, both the carbon nanotube 204 and nanopore 207are coated with organic monolayers (i.e., organic coatings 205 and 206respectively). In the case of the carbon nanotube 204, the organiccoating 205 is achieved by reaction of the carbon nanotube 204 withbifunctional diazonium salts which have either alcohol or amine groups,and the organic coating 206 inside the nanopore 207 is a bifunctionalmolecule having a functional group which forms a bond inside thenanopore 207 wall (e.g., hydroxamic acid or phosphonic acid) and thesecond exposed functionality which forms a covalent bond throughcondensation with exposed functionality of the carbon nanotube 204 (e.g.carboxylic acid). For example, the nanopore 207 can be coated with4-carboxybenzylphosphonic acid by immersion of the nanopore 207 in adilute (1-5 mmolar) solution of the latter in water or alcohol. Afterrinsing with the same solvent, the inside of the nanopore 207 (the wallor portion of the nanopore wall must be of metal oxide or nitride) iscoated with a self assembled monolayer of 4-carboxybenzylphosphonic acidin a way that phosphonic acid forms covalent bonds with metal oxide ornitride and exposes the carboxylic acid functionality. In the secondstep, the functionalized carbon nanotube 204 having an alcohol or aminefunctionality is pulled inside the nanopore 207 and with the aid of adehydrating agent (which must be present in the salt solution) the twofunctionalities of carboxylic acid and alcohol (or amine) undergodehydration to form carboxylic ester (or carboxamide) resulting inimmobilization of carbon nanotube 204. An example of the dehydratingagent (which is also water soluble and can be used in this environment)is N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride. InFIGS. 4B and 4C, after the organic coating 205 and 206 react with eachother to form an ester or amide, the joined coatings are designated as270.

For the reaction (corresponding to FIGS. 2A, 2B, and 2C) when thenanopore 207 is uncoated and the carbon nanotube 204 is coated (withorganic coating 205 as discussed above), the organic coating 205 isachieved by the reaction of a bifunctional aryldiazonium salt. Forexample, 4-aminobenzylphosphonic acid is treated with nitrosoniumtetrafluoroborate to form corresponding diazonium salt. A solution ofthis diazonium salt is added to an aqueous dispersion of carbonnanotubes containing small (0.1-1%) amount of surfactant (e.g., sodiumdodecylsulfate or sodium cholate). After stiffing at room temperaturefor 30 minutes, the carbon nanotube 204 is functionalized withbenzylphsophonic acid. An aqueous solution of the functionalized carbonnanotube 204 obtained above containing 0.1% anionic surfactant is pulledinto nanopore 207 (as shown in FIGS. 2A, 2B, 2C) where the phosphonicacid functionality reacts with the surface of metal oxide (or nitride)inside the nanopore 207 to form a covalent bond.

For the reaction (corresponding to FIGS. 3A, 3B, and 3C) when thenanopore 207 is coated (with organic coating 215) and the carbonnanotube 204 is uncoated, the inside of the nanopore 207 is coated(organic coating 215) with bifunctional arylamine, e.g.,4-aminophenylhydroxamic acid by immersion of the nanopore 207 in adilute (1-5 mmolar) solution of the amine in ethanol. After sometime(e.g., 1-24 hours, preferably 1-2 hours) the substrate (forming thenanopore 207) is removed and rinsed with ethanol. This step results inself assembly of 4-aminophenylhydroxamic acid on the inside wall ofnanopore 207 by formation of covalent bonds through hydroxamic acidfunctionality with metal oxide (or nitride) of the nanopore 207 andexposing arylamine functionality. Next, the coated nanopore 207 istreated with a dilute solution of nitrosonium ion (e.g., a solution ofnitrosonium tetrafluoroborate or dilute solution of sodium nitrite indilute hydrochloric acid) resulting in transformation of the amine groupto diazonium salt. In the last step, the uncoated carbon nanotube 204 insalt solution is pulled into the coated nanopore 207 which will reactwith diazonium functionality of the self assembled monolayer and formcarbon-carbon bond to immobilize the carbon nanotube 204 inside thenanopore 207.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, element components,and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated

The flow diagrams depicted herein are just one example. There may bemany variations to this diagram or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

While the exemplary embodiments of the invention have been described, itwill be understood that those skilled in the art, both now and in thefuture, may make various improvements and enhancements which fall withinthe scope of the claims which follow. These claims should be construedto maintain the proper protection for the invention first described.

1. A method of embedding a nanotube in a nanopore, the methodcomprising: configuring a reservoir comprising a membrane separating thereservoir into a first reservoir part and a second reservoir part, thenanopore being formed through the membrane for connecting the first andsecond reservoir parts; and filling the nanopore, the first reservoirpart, and the second reservoir part with an ionic fluid; wherein a firstelectrode is dipped in the first reservoir part; wherein a secondelectrode is dipped in the second reservoir part; and wherein thenanotube is driven into the nanopore by a voltage bias applied to thefirst and second electrodes, to cause an inner surface of the nanoporeto form a covalent bond to an outer surface of the nanotube via anorganic coating.
 2. The method of claim 1, further comprising coatingthe inner surface of the nanopore with the organic coating to form thecovalent bond to the outer surface of the nanotube.
 3. The method ofclaim 1, further comprising coating the outer surface of the nanotubewith the organic coating to form the covalent bond to the inner surfaceof the nanopore.
 4. The method of claim 1, further comprising coatingthe inner surface of the nanopore with the organic coating; coating theouter surface of the nanotube with the organic coating; and wherein theorganic coating on the inner surface of the nanopore and the organiccoating on the outer surface of the nanotube cause the covalent bond inresponse to driving the nanotube into the nanopore.
 5. The method ofclaim 1, further comprising coating the inner surface of the nanoporewith the organic coating; and coating the outer surface of the nanotubewith another organic coating; wherein the organic coating on the innersurface of the nanopore and the another organic coating on the outersurface of the nanotube form the covalent bond while the nanotube isdriven into the nanopore.
 6. The method of claim 1, wherein the covalentbond via the organic coating causes the nanotube to be attached to thenanopore in the membrane.
 7. The method of claim 6, wherein both sidesof the membrane are processed such that a height of the nanotubecorresponds to a height of a layer of the membrane.